This invention is directed to reaction products of mercapto-thiadiazoles, mercaptans and thionyl chloride as zinc/phosphorus-free antiwear agents and antioxidants.
Replacement of zinc phosphorodithioates by zinc/phosphorus-free antiwear additives in circulating oils, gear oils and various other lubricating systems is considered highly desirable because of environmental considerations and the potential electrolytic corrosivity of zinc salts. An additive system which in addition to antiwear activity exhibits antioxidant activity and copper passivation is highly desirable. The condensates of the present invention provide outstanding FZG gear performance, low Four-ball wear and antioxidant activity. Furthermore, they contain no corrosive sulfur.
Various reaction products of mercapto and dimercapto-thiadiazoles (DMTD) are known in the art. For example, reaction products of 2,5-dimercapto-1,3,4-thiadiazole are disclosed in U.S. Pat. No. 4,128,510 as being useful as cross-linking agents for halogen-containing polymers. U.S. Pat. No. 4,382,869 discloses reaction products of mercaptothiadiazoles with hydroxyl-containing compounds as friction reducing and corrosion-inhibiting additives for lubricant oils. Although reaction products containing the mercapto-1,3,4-thiadiazole structure has found widespread use as lubricant antioxidants and metal passivators, the compositions and the utility of the reaction products described in this patent application are believed to be unknown heretofore in the art.